Using libguestfs remotely with Python and rpyc

libguestfs has high quality Python bindings. Using rpyc you can make a remote libguestfs server with almost no effort at all.

Firstly start an rpyc server:

$ /usr/lib/python2.7/site-packages/rpyc/servers/classic_server.py
[SLAVE      INFO       13:21:17 tid=140019939981120] server started on 0.0.0.0:18812
[SLAVE      INFO       13:21:17 tid=140019784894208] started background auto-register thread (interval = 60)
[REGCLNT    INFO       13:21:17] registering on 255.255.255.255:18811
[REGCLNT    WARNING    13:21:19] no registry acknowledged

Now, possibly from the same machine or some other machine, you can connect to this server and use Python objects remotely as if they were local:

$ python
Python 2.7.3 (default, Aug  9 2012, 17:23:57) 
[GCC 4.7.1 20120720 (Red Hat 4.7.1-5)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import rpyc
>>> c = rpyc.classic.connect('localhost')

You can now create a libguestfs handle, following the example here.

>>> g = c.modules.guestfs.GuestFS()
>>> g.version()
{'release': 36L, 'major': 1L, 'minor': 21L, 'extra': 'fedora=20,release=1.fc20,libvirt'}
>>> g.add_drive('/dev/fedora/f18x64', readonly=True)
>>> g.launch()
>>> roots = g.inspect_os()
>>> g.inspect_get_product_name(roots[0])
'Fedora release 18 (Spherical Cow)'
>>> g.inspect_get_mountpoints(roots[0])
[('/', '/dev/mapper/fedora-root'), ('/boot', '/dev/sda1')]

As you can see, the g object is transparently remoted without you needing to do anything.

Brian Steven’s keynote at OpenStack Summit

Brian is Red Hat’s CTO, and hence my boss’s boss’s boss (or something like that). This is a pretty good (and honest) talk about Red Hat’s plans for OpenStack.

Edit: By the way, the thumbnail (the one I see at any rate) is not Brian.

Amazon (or just “online ordering”) rant

There are some items which are just not possible to order online any more, assuming you want something of minimal quality. These include:

1. chargers for mobile phones — all now fake as far as I can tell
2. batteries for older mobile phones — second hand, dead, fake, or simply the wrong battery
3. consumer cables, like USB to micro USB
4. convection heaters — didn’t expect this, but I can’t find a reliable one (for the new office) online

That’s not counting the stuff where it’s still just about possible to get non-fake stuff, but it’s a crapshoot, eg. computer memory, hard disks, batteries, flash memory.

Using rsync with libguestfs

Since libguestfs 1.20 it has been possible to use rsync to upload or download files to a disk image incrementally. This is one way to do backups, but note that it won’t work on live guests unless you take a snapshot.

rsync involves using a network connection into or out of the appliance, and is therefore a lot more involved to set up. The script below shows one way to do this, by running an rsync daemon on the host, and letting the libguestfs appliance connect to it.

The script runs rsync inside the appliance, copying /home from the attached disk image out to /tmp/backup on the host. If the operation is repeated, then only incrementally changed files will be copied out. (To incrementally delete files on the target, add the deletedest:true flag).

Note you will need to open port 2999 on your host’s firewall for this to work.

#!/bin/bash -

set -x

# The target directory.
mkdir -p /tmp/backup

# Create the daemon.
rm -f /tmp/rsyncd.pid

cat <<EOF > /tmp/rsyncd.conf
port = 2999
pid file = /tmp/rsyncd.pid

[backup]
  path = /tmp/backup
  use chroot = false
  read only = false
EOF

rsync --daemon --config=/tmp/rsyncd.conf

# Run guestfish and attach to the guest.
guestfish --ro --network -a /dev/fedora/f19rawhidex32 -i <<EOF
trace on
rsync-out /home rsync://rjones@192.168.122.1:2999/backup archive:true
EOF

# Kill the rsync daemon.
kill `cat /tmp/rsyncd.pid`

Garden office – undercoat done

Inside there’s a ring for sockets and a lighting circuit. The windows and doors are pre-made double-glazed units.

Garden office – roof going on

Garden office – construction continues

Update: Further progress this morning …